System for positioning a cutting guide in knee surgery

ABSTRACT

A system is provided for positioning a cutting guide on a femur of a knee to make a cut along a distal end of the femur during knee surgery. The system may generally include an adjustable femoral attachment member configured to attach to a cut distal end of the femur, a cutting guide removably attachable to the femoral attachment member and configured to guide a surgical saw to make an additional cut on the distal end of the femur, and a force sensor for positioning between the femoral attachment member and a proximal end of a tibia of the knee. The force sensor may include a medial portion for sensing a medial force in the knee and a lateral portion for sensing a lateral force in the knee.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation in part of U.S. patentapplication Ser. No. 12/609,666, filed Oct. 30, 2009, which claimspriority to U.S. Provisional Patent Application Ser. No. 61/109,770,filed Oct. 30, 2008. The full disclosures of these two applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical surgical devices,systems, and methods. More specifically, the invention relates todevices, systems and methods for facilitating knee surgery procedures,in particular, knee replacement procedures.

2. Description of the Related Art

The knee is generally defined as the point of articulation of the femurwith the tibia. Structures that make up the knee include the distalfemur, the proximal tibia, the patella, and the soft tissues within andsurrounding the knee joint, the soft tissues including the ligaments ofthe knee. The knee is generally divided into three compartments: medial(the inside part of the knee), lateral (the outside part of the knee),and patello-femoral (the joint between the kneecap and the femur). Themedial compartment comprises the medial joint surfaces of the femur,tibia, and the meniscus wedged therebetween. The lateral compartmentcomprises the lateral joint surfaces of the femur, tibia, and themeniscus wedged therebetween. The patellofemoral compartment comprisesthe joint between the undersurface of the kneecap or patella and thefemur. Four ligaments are especially important in the stability,alignment and functioning of the knee—the anterior cruciate ligament,the posterior cruciate ligament, the medial collateral ligament, and thelateral collateral ligament. In an arthritic knee, protective cartilageat the point of articulation of the femur with the tibia is often wornaway, allowing the femur to directly contact the tibia. Thisbone-on-bone contact can cause significant pain, discomfort, anddisability for a patient and will often necessitate knee replacement orknee arthroplasty.

Knee arthroplasty involves replacing the diseased and painful jointsurface of the knee with metal and plastic components shaped to allownatural motion of the knee. Knee replacement may be total or partial.Total knee replacement surgery, also referred to as total kneearthroplasty (“TKA”), involves a total replacement of the distal end ofthe femur, the proximal end of the tibia, and often the inner surface ofthe patella with prosthetic parts. Cuts are made on the distal end ofthe femur and the proximal end of the tibia. Prosthetic parts are thenattached. The prosthetic parts create a stable knee joint that movesthrough a wide range of motion. The replacement of knee structures withprosthetic parts allows the knee to avoid bone-on-bone contact andprovides smooth, well-aligned surfaces for joint movement.

In knee replacement surgeries, it is often vital to restore themechanical alignment of the knee, i.e., the proper alignment of themechanical axes of the femur and tibia with each other. Many methods anddevices currently are used to restore the mechanical alignment of theleg. These methods and devices are typically used during Total KneeReplacement surgery and include alignment rods, e.g., intramedullary andextramedullary rods, surgical navigation systems, and CT and or MRIbased “bone morphing” or “shape-fitting” technologies. Generally,empirical anatomical landmarks are used in these methods. Theseanatomical landmarks are either directly/mechanically observedintra-operatively, or indirectly relied upon, serving as the foundationof a computer generated reference method. Reference geometry andphysical or virtual measurements are often used to ultimately alignbone-cutting guides or templates which facilitate bone resections (madewith a surgical saw blade). These bone resections will typicallyproperly orient a knee prosthesis in the correct location/alignment.Generally, none of these methods directly take the condition ortendencies of the soft-tissue structures, such as the lateral collateraland medial collateral ligaments, about the knee into consideration.

Historically, surgeons performing total knee replacement surgery in thelate 1970s and early 1980s would typically first resect the proximaltibia, creating a flat surface perpendicular to the shaft of the tibia.The leg was then brought to extension. Spacer blocks were shoved betweenthe resected tibia and the uncut distal femur. The spacer blocks wereselected from various thicknesses in order to distract the knee jointspace to the extent the ligaments about the knee were somewhat taut.Once the knee joint was distracted to that taut condition, a distalfemoral cutting guide was positioned in a way to yield a distal femoralbone cut parallel to the tibial cut. It was believed that a distalfemoral bone cut, using this method of distracting the joint spacebetween the tibia and femur, would yield proper alignment of themechanical axis of the leg. This method would often prove successful aspracticed by a skilled surgeon and in the case of “passive deformities”of the knee. However, the distraction method would typically not haveany accurate means of determining ligament forces between the medialside of the knee and/or the lateral side of the knee. As such, properalignment would often not be restored. Additionally, the method of firstmaking a proximal tibial bone resection and then making a distal femoralbone resection parallel to the tibial bone resection did not restoreproper alignment of the leg in the case of “fixed deformities” of theknee. The case of “fixed deformities” of the knee would otherwiserequire ligament releases to restore proper alignment of the knee.Accordingly, many early knee replacement surgeons determined that thetibial bone resection and the distal femoral bone resections should bemade independent of each other.

As technology has advanced, including the introduction of CT scannersand MRI technology, the thought of computerized bone morphing has gainedpopularity as a means to accurately place cutting guides. The cuttingguides, in turn, are be used in efforts to place prosthetic kneeimplants in a position in which the knee is properly aligned. Earlystudies have not found these bone morphing technologies always accurate,reporting proper alignment of the leg was not restored. However, aproper patient selection, e.g., patients with mild, passive deformitiesof the knee, might be viable candidates for bone morphing technology,assuming those patients/deformities could be properly corrected bysimple anatomical referencing, as determined by a CT or MRI scan.

However, bone morphing technology is often costly, requiring a CT or MRIscan to determine any given patient's anatomy. Electronic images fromsuch scans must be “filtered” by a computer technician. The “filtered”scan data must be electronically conveyed to some type of fabricationmachine, such as a CNC Machining Center or a Rapid Prototype Machine.Ultimately, “shape-matching” and “patient specific” cutting guides mustbe produced and delivered into surgery.

As such, there is a clear need for systems, devices, and methods of kneesurgery that can help surgeons quickly, accurately, and cost-effectivelyposition the distal femoral cutting guide, thus restoring properalignment and soft-tissue balance of the leg during total kneereplacement surgery.

Non-patent literature which may be of interest may include: Murray,David G., “Variable Axis™ Total Knee Surgical Technique,” HowmedicaSurgical Techniques, Howmedica Inc. 1977; Mihalko, W H et al.,“Comparison of Ligament-Balancing Techniques During Total KneeArthroplasty,” Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003,132-135; Eckhoff, D G et al., “Three-Dimensional Morphology andKinematics of the Distal Part of the Femur Viewed in Virtual Reality,Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003, 97-104; and Ries, MD, et al., “Soft-Tissue Balance in Revision Total Knee Arthroplasty,”Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003, 38-42. Patents ofinterest may include U.S. Pat. Nos. 4,501,266; 4,646,729; 4,703,751;4,841,975; 5,116,338; 5,417,694; 5,540,696; 5,597,379; 5,720,752;5,733,292; 5,800,438; 5,860,980; 5,911,723; 6,022,377 and 6,758,850.Patents applications of interest may include co-assigned U.S. patentapplication Ser. No. 10/773,608, now U.S. Pat. No. 7,442,196, entitled“Dynamic Knee Balancer” (Attorney Docket No. 021976-000200US); Ser. No.10/973,936, now U.S. Pat. No. 7,578,821 entitled “Dynamic Knee Balancerwith Pressure Sensing” (Attorney Docket No. 021976-000210US); Ser. No.11/149,944 now U.S. Patent Publication Application No. 2005/0267485 A1entitled “Dynamic Knee Balancer with Opposing Adjustment Mechanism”(Attorney Docket No. 021976-000220US); 61/090,535 entitled “SensingForce During Partial and Total Knee Replacement Surgery” (AttorneyDocket No. 021976-000800US); and 61/107,973 entitled “Dynamic KneeBalancing for Revision Procedures” (Attorney Docket No.021976-000700US), the entire contents of each of which are incorporatedherein by reference.

SUMMARY OF THE INVENTION

The present invention provides devices, systems, and methods forfacilitating a surgery performed on a knee, particularly by facilitatingthe aligning of the knee during a total knee replacement surgery. Afemoral assembly is engaged with a distal femur and placed in the gapbetween the distal femur and proximal tibia. The femoral assemblycomprises a stationary portion, an adjustable medial portion, and anadjustable lateral femoral portion. The positions of the medial andlateral femoral portions relative to the stationary portion can beseparately adjusted to adjust the varus-valgus alignment of the knee,e.g., the angle between the femur and tibia, as well as the tension inthe soft tissues adjacent the knee. Additionally, the femoral assemblycomprises adjustable posterior members that fill the posterior capsuleof the knee with a thickness similar to the prosthetic femoral implant.Typically, a force sensor will be provided to sense the forces in themedial portion of the knee and the lateral portion of the knee, and themedial and lateral femoral portions will be adjusted so that the sensedforces are balanced. A visual display may be provided to show thesurgeon the sensed forces. In addition, a thickness adapter may beprovided to removable attach to the force sensor to fill the spacebetween the femur and tibia to the point force readings are obtained.The alignment of the knee can be visually verified using a kneealignment verification member coupled to the femoral assembly, andfurther verified by angular graduation markings placed upon the femoralstationary portion. The knee alignment verification member may emitlaser beams along the mechanical axes of the femur and tibia. Or,alignment rods which align along the mechanical axes of the femur andtibia may be coupled to the knee alignment verification member. Thealignment of the knee can be verified using with the laser beams and/orthe alignment rods. When the knee is properly aligned, placement pinsmay be positioned in the distal femur guided by the femoral assembly.The femoral assembly can then be removed and a cutting guide can bepositioned on the distal femur based on the position of the placementpins. A cut parallel to a previously made cut on the tibia can then bemade on the distal femur. A prosthetic knee placed on these cuts willmaintain the proper alignment of the knee.

In a first aspect, the invention provides a system for aligning the kneeduring a surgical procedure on the knee. The system comprises a femoralassembly that is removably engaged with a distal femur. The femoralassembly includes a stationary femoral portion, an adjustable medialfemoral portion (which is coupled to the stationary femoral portion),and an adjustable lateral femoral portion (which is coupled to thestationary femoral portion. A knee alignment verification member iscoupled with the stationary femoral portion of the femoral assembly andprovides visual confirmation of a femoral and tibial mechanical axes ofthe knee. A force sensor is coupled with the stationary femoral portionof the femoral assembly. The force sensor comprises a medial portion forsensing a first force in a medial portion of the knee and a lateralportion for sensing a second force in a lateral portion of the knee.

In one embodiment, the knee alignment verification member means includesa laser knee alignment verification member is coupled to the stationaryfemoral portion. The laser knee alignment provides a first laser beamoriented along the femoral axis of the knee and a second laser beamoriented along the tibial axis of the knee.

In some embodiments, the knee alignment verification member includes amechanical knee alignment verification assembly. The mechanical kneealignment verification assembly includes a knee alignment hub. A firstrod is coupled with the knee alignment hub to be oriented along thefemoral axis of the knee and a second rod is coupled with the kneealignment hub to be oriented along the tibial axis of the knee.

In an embodiment, the adjustable medial portion includes a medial paddleand the adjustable femoral portion includes a lateral paddle.

In still other embodiments, the position of the adjustable medialfemoral portion relative to the stationary femoral portion isadjustable. The position of the adjustable lateral femoral portionrelative to the stationary femoral portion is adjustable.

In other embodiments, the adjustable medial femoral portion and theadjustable lateral femoral portion are separately adjustable.

In some embodiments, a medial rotatable screw couples the adjustablemedial femoral portion with the stationary femoral portion. A lateralrotatable screw couples the adjustable lateral femoral portion with thestationary femoral portion.

In some embodiments, rotating the medial rotatable screw adjusts theposition of the adjustable medial femoral portion relative to thestationary femoral portion. Rotating the lateral rotatable screw adjuststhe position of the adjustable lateral femoral portion relative to thestationary femoral portion.

In some embodiments, the force sensor comprises a force sensing elementselected from the group consisting of piezoelectric sensors, forcesensing resistors, force sensing capacitors, strain gages, load cells,and pressure sensors.

In still other embodiments, a processor is coupled with the force sensorfor processing sensed force data into usable data and for providing thedata to a user. A visual display is coupled with the processor andadapted to display the usable data.

In some embodiments, the visual display displays usable datarepresenting a first force sensed in the medial portion of the knee anda second force sensed in the lateral portion of the knee.

In some embodiments, the system for aligning a knee during knee surgeryincludes a plurality of locating pins. The stationary femoral portiondefines at least one medial aperture for positioning at least onelocating pin on the distal femur and at least one lateral aperture forpositioning at least a second locating pin on the distal femur.

In some embodiments of the invention, a cutting guide is removablyengaged with the distal femur. The cutting guide is positioned relativeto the distal femur based on the position of at least one first locatingpin and the at least a second locating pin.

In some embodiments, the force sensor is removably coupled to athickness adapter. The adapter fills the space between the femur andtibia.

In some embodiments, the adjustable medial femoral portion and theadjustable lateral femoral portion include a medial fulcrum and lateralfulcrum. The fulcrums are positioned against the provisionally cutdistal femur when the distal femoral alignment assembly is mountedagainst the distal femur. In other embodiments, a bone interface plateis disposed between the fulcrums and the distal femur.

In a second aspect, the invention provides a method for aligning theknee during a surgical procedure on the knee including engaging afemoral assembly with a distal femur. The femoral assembly includes astationary femoral portion, an adjustable medial femoral portion(coupled to the stationary femoral portion), and an adjustable lateralfemoral portion (coupled to the stationary femoral portion). A forcesensor is coupled with the stationary femoral portion of the femoralassembly. A first force is sensed in a medial portion of the knee and asecond force is sensed in the lateral portion of the knee using thecoupled force sensor. The position of the adjustable medial femoralportion can be adjusted separately relative to the stationary femoralportion and the position of the adjustable lateral femoral portion isseparately adjustable relative to the stationary femoral portion basedon the sensed first and second forces to align a femoral and tibialmechanical axes of the knee. The alignment of the femoral and tibialmechanical axes of the knee are visually confirmed using a kneealignment verification assembly coupled with the stationary femoralportion of the femoral assembly.

In one embodiment, a method for aligning the knee during a surgicalprocedure on the knee comprises coupling a mechanical knee alignmentverification assembly with the stationary femoral member of the femoralassembly. A first alignment rod of the mechanical knee alignmentverification assembly is aligned along the femoral axis of the knee anda second alignment rod of the mechanical knee alignment verificationassembly is aligned along the tibial axis of the knee. The femoral andtibial mechanical axes of the knee is visually confirmed by thealignment of the first alignment rod and the second alignment rodrelative to each other.

In another embodiment, a laser knee alignment verification member iscoupled with the stationary femoral member of the femoral assembly, Afirst laser beam from the laser knee alignment verification member isaligned along the femoral mechanical axis of the knee and a second laserbeam from the laser knee alignment verification member is aligned alongthe tibial mechanical axis of the knee along the tibial axis of theknee, The alignment of the femoral and tibial mechanical axes of theknee is visually confirmed by the alignment of the first laser beam andthe alignment of the second laser beam relative to each other.

In some embodiments, the positions of the adjustable medial femoralportion relative to the stationary femoral portion and of the adjustablelateral femoral portion relative to the stationary femoral portion areadjusted based on the sensed first force and the sensed second force sothat the first and second forces are balanced.

In some embodiments, the first force in a medial portion of the knee issensed and a second force in a lateral portion of the knee is sensedusing the coupled force sensor. This includes transmitting a voltage toa sensor element of a thin force sensing portion of the force sensor andmeasuring the voltage after it has passed through the sensor element.The percentage of the voltage that passed through the sensor element isdetermined relative to the voltage transmitted to the sensor element.The measured force is derived from the percentage.

In yet another embodiment, the sensed first force and the sensed secondforce is visually displayed by a display coupled to the force sensor.

In some embodiments, separately adjusting the position of the adjustablemedial femoral portion relative to the stationary femoral portion andthe position of the adjustable lateral femoral portion relative to thestationary femoral portion comprises rotating at least one of a lateralrotatable screw coupling the adjustable lateral femoral portion to thestationary femoral portion and a medial rotatable screw coupling theadjustable medial femoral portion to the stationary femoral portion.

In some embodiments, the stationary femoral portion defines at least onemedial aperture and at least one lateral aperture. The method furtherincludes positioning at least one locating pin on the distal femur basedon at least one medial aperture and positioning at least a secondlocating pin on the distal femur based on the at least one lateralaperture.

In an embodiment, the femoral assembly is disengaged with the distalfemur and engages a distal femoral cutting guide with the distal femur.The distal femoral cutting guide is positioned relative to the distalfemur based on the position of at least one first and at least onesecond locating pins.

In some embodiments, cuts are made on the distal femur based on theposition of the distal femoral cutting guide.

In another aspect, the invention provides a method for aligning a legduring knee surgery. The leg has a femur and a tibia. The femur has amechanical axis, a distal end and a proximal end. The tibia has amechanical axis, a distal end and a proximal end. The method of aligningthe leg includes engaging a femoral assembly with the provisionally cutdistal end of the femur. The femoral assembly includes a stationaryfemoral portion, an adjustable medial femoral portion that has a medialpivot fulcrum coupled to the stationary femoral portion, and anadjustable lateral femoral portion that has a lateral pivot fulcrumcoupled to the stationary femoral portion. A force sensor is coupledwith the stationary femoral portion of the femoral assembly. A medialposterior member is reversibly coupled to the medial side of thestationary femoral portion. A lateral posterior member is reversiblycoupled to the lateral side of the stationary femoral portion. Themedial member abuts the medial posterior femur and the lateral memberabuts the lateral posterior femur. A first force is sensed in a medialportion of the knee and a second force is sensed in the lateral portionof the knee using the force sensor. The position of the adjustablemedial femoral portion is adjusted relative to the stationary femoralportion and the position of the adjustable lateral femoral portion is(separately) adjusted relative to the stationary femoral portion basedon the sensed first and second forces to align the femoral and tibialmechanical axes of the knee. The alignment of the femoral and tibialmechanical axes of the knee is visually confirmed using a knee alignmentverification assembly which is coupled with the stationary femoralportion of the femoral assembly.

In one embodiment, the medial member abuts the medial posterior femurand the lateral member abuts the lateral posterior femur when the leg isfully extended.

In some embodiments, the medial and lateral fulcrums determine fixeddistance points to adjust an angle.

In some embodiments, a bone interface plate is disposed between theadjustable medial and lateral femoral portions and the distal femur.

In another aspect, a system for positioning a cutting guide on a femurof a knee to make a cut along a distal end of the femur during asurgical procedure on the knee may include: an adjustable femoralattachment member configured to attach to a cut distal end of the femura cutting guide removably attachable to the femoral attachment memberand configured to guide a surgical saw to make an additional cut on thedistal end of the femur; and a force sensor for positioning between thefemoral attachment member and a proximal end of a tibia of the knee,wherein the force sensor comprises a medial portion for sensing a medialforce in the knee and a lateral portion for sensing a lateral force inthe knee. The femoral attachment member may include: a medial elevatorfor increasing an amount of space between a medial portion of thefemoral attachment member and the cut distal end of the femur; a lateralelevator for creating space between a lateral portion of the femoralattachment member and the cut distal end of the femur; and a singleadjustment member configured to adjust both the medial and lateralelevators;

In some embodiments, the system may also include one or more inserts forpositioning between the force sensor and the femoral attachment memberin the knee. The system may also optionally include multiple pins forattaching the cutting guide to the femur and/or multiple screws forattaching the femoral attachment member to the femur. In one embodiment,the femoral attachment member may include at least two screw holes on adistal-facing surface for accepting the screws. Optionally, the systemmay also include an indicator on the distal-facing surface forindicating an angle of resection to which the cutting guide has beenadjusted.

The system may further include an adjustment device for adjusting thefemoral attachment member. For example, the adjustment device in oneembodiment may be a wrench configured to turn the adjustment member inone direction to adjust the medial elevator and in an opposite directionto adjust the lateral elevator. In some embodiments, the system may alsoinclude a slide member removably coupled with the cutting guide so thatthe cutting guide and slide member can slide onto the femoral attachmentmember to contact an anterior side of the femur.

In some embodiments, the femoral attachment member may be configured tobe attached to the cut distal end of the femur while the knee is inflexion. In such embodiments, the femoral attachment member may also beconfigured to remain attached to the cut distal end of the femur whilethe knee is moved from flexion to extension. In some embodiments, thesystem may further include a display coupled with the sensor, configuredto display a first indicator representing the medial force and a secondindicator representing the lateral force.

In another aspect, a method for positioning a cutting guide on a femurof a knee to make a cut along a distal end of the femur during asurgical procedure on the knee may involve: attaching an adjustablefemoral attachment member with a cut distal end of the femur;positioning a force sensor on a cut proximal end of a tibia of the knee;attaching the cutting guide to the femoral attachment member; adjustingthe femoral attachment member, using a single adjustment member of thefemoral attachment member, to elevate at least one of a medial side anda lateral side of the femoral attachment member relative to the cutdistal end of the femur to approximately balance medial and lateralforces displayed on a display coupled with the sensor, wherein adjustingthe femoral attachment member changes a position of the cutting guiderelative to the femur; and attaching the cutting guide to the femur.

In some embodiments, attaching the femoral attachment member may involveadvancing two screws through holes in the attachment member and into thecut distal end of the femur while the knee is in flexion. Optionally,the method may also include positioning an insert between the forcesensor and the femoral attachment member. The method may further involvemoving the knee into extension while the femoral attachment memberremains attached to the femur and before adjusting the femoralattachment member. In such an embodiment, the cutting guide may remainattached to the femur while the knee is in extension. In someembodiments, attaching the cutting guide involves pinning the cuttingguide to the femur using multiple pins.

The method may further involve moving the knee back into flexion afterthe cutting guide is attached. In one embodiment, the method may furtherinclude viewing a resection angle indicator on a distal surface of thefemoral attachment member while the knee is in flexion, where theresection angle indicator indicates approximately an angle of resectionof the distal femur based on a position of the cutting guide. In someembodiments, attaching the cutting guide to the femoral attachmentmember may involve sliding the cutting guide, attached to a slidemember, onto the femoral attachment member until the cutting guidecontacts a cut anterior surface of the femur. Optionally, the method mayfurther involve, before attaching the cutting guide to the femoralattachment member, attaching the slide member to the cutting guide. Forexample, attaching the slide member to the cutting guide may involvetightening a first screw using an adjustment device, and adjusting thefemoral adjustment member may involve turning a second screw using thesame adjustment device.

Optionally, the method may further involve, before attaching the femoraladjustment member, making initial cuts on the distal end of the femur,an anterior side of the femur and a posterior side of the femur. In someembodiment, the single adjustment member may be a screw, and adjustingthe femoral adjustment member may involve using an adjustment device toturn the screw in a first direction to adjust the medial side of theadjustment member and in a second direction to adjust the lateral sideof the adjustment member. In some embodiments, the method may alsooptionally involve removing the femoral attachment member from the femurand the sensor from the tibia and cutting the distal end of the femur,using the attached cutting guide. In some embodiments, the method mayfurther include removing a slide member attached to the cutting guidebefore cutting the distal end of the femur.

In another aspect, a method for making a cut on a distal end of a femurduring a surgical procedure on a knee may include: attaching anadjustable femoral attachment member with the distal end of the femur onwhich initial distal, anterior and posterior cuts have previously beenmade, while the knee is in flexion; positioning a force sensor coupledwith an insert on a cut proximal end of a tibia of the knee; sliding acutting guide onto the femoral attachment member until it contacts a cutanterior side of the femur; tightening the cutting guide onto thefemoral attachment member; moving the knee into extension; adjusting thefemoral attachment member, using a single adjustment member of thefemoral attachment member, to balance medial and lateral forcesdisplayed on a display coupled with the sensor, wherein adjusting thefemoral attachment member changes a position of the cutting guiderelative to the femur; attaching the cutting guide to the femur; movingthe knee into flexion; removing the femoral attachment member from thefemur; and making the cut on the distal end of the femur, using thecutting guide.

In some embodiments, adjusting the femoral attachment member may involveturning the single adjustment member using an adjustment device in atleast one of a first direction, to adjust the medial force, and a seconddirection, to adjust the lateral force. In some embodiments, tighteningthe cutting guide may involve using the adjustment device to tighten ascrew attaching the cutting guide to the femoral attachment member. Insome embodiments, sliding the cutting guide onto the femoral attachmentmember may involve sliding a slide member attached to the cutting guidealong the femoral attachment member. In these embodiments, the methodmay optionally further involve removing the slide member from thecutting guide before making the cut on the distal end of the femur. Themethod may also further involve viewing a resection angle indicator onthe femoral attachment member after moving the knee into flexion toapproximate a resection angle before making the cut. In someembodiments, the method may also involve removing the sensor and theinsert from the tibia before making the cut on the distal end of thefemur.

In another aspect, a device for positioning a cutting guide on a femurof a knee during a surgical procedure on the knee, may include: astationary femoral member that attaches to a cut distal end of thefemur; an adjustable femoral member moveably attached to the stationaryfemoral member; a medial elevator for creating space between thestationary and adjustable femoral members closer to a medial edge of thedevice than a lateral edge of the device; a lateral elevator forcreating space between the stationary and adjustable femoral memberscloser to the lateral edge of the device than the medial edge of thedevice; and a single adjustment member configured to adjust both themedial and lateral elevators.

In some embodiments, the device may further include a cutting guideremovably attachable to the adjustable femoral member and configured toguide a surgical saw to make an additional cut on the distal end of thefemur. In some embodiments, the device may include a force sensor forpositioning between the adjustable femoral member and a proximal end ofa tibia of the knee. The force sensor may include a medial portion forsensing a medial force in the knee and a lateral portion for sensing alateral force in the knee. Some embodiments may further include adisplay coupled with the sensor and configured to display a firstindicator representing the medial force and a second indicatorrepresenting the lateral force. Some embodiments may also furtherinclude an insert for positioning between the force sensor and thefemoral attachment member in the knee. In some embodiments, the devicemay include multiple screws for attaching the stationary femoral memberto the femur.

In some embodiments, the device may include an indicator on adistal-facing surface of the adjustable femoral member for indicating anangle of resection to which the cutting guide has been adjusted. Thedevice may also include an adjustment device for adjusting the medialand lateral elevators via the single adjustment member. In someembodiments, the adjustment device may include a wrench configured toturn the adjustment member in one direction to adjust the medialelevator and in an opposite direction to adjust the lateral elevator. Insome embodiments, the single adjustment member may include a slidingportion that slides in a first direction to elevate the medial elevatorand in a second, opposite direction to elevate the lateral elevator. Inmany embodiments, the device may be configured to be attached to the cutdistal end of the femur while the knee is in flexion. In someembodiments, the femoral attachment member may be configured to remainattached to the cut distal end of the femur while the knee is moved fromflexion to extension.

These and other aspects and embodiments are described in greater detailbelow, in reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a distal femoral alignment componentassembly according to embodiments of the invention.

FIG. 2 shows a top view of the unadjusted distal femoral alignmentassembly of FIG. 1.

FIG. 3 shows a top view of the adjusted distal femoral alignmentassembly of FIG. 1.

FIG. 4 shows a perspective view of the unadjusted distal femoralalignment assembly of FIG. 1.

FIG. 5 shows a perspective view of the adjusted distal femoral alignmentassembly of FIG. 1.

FIGS. 6 and 7 shows perspective views of a knee alignment systemaccording to embodiments of the invention.

FIG. 8 shows a visual display of a knee alignment system according toembodiments of the invention.

FIGS. 9-10 show a side view of a knee alignment system, including thedistal femoral alignment component and the force sensor coupledtogether, being placed in the gap.

FIGS. 11-12 show a perspective view of a knee alignment system,including the distal femoral alignment component and the force sensorcoupled together, being placed in the gap.

FIGS. 13-23 show a method of aligning a knee during surgery according toembodiments of the invention.

FIG. 24A-B shows exploded views of a knee alignment system according toembodiments of the invention.

FIG. 25 shows a top view of the unadjusted distal femoral alignmentassembly.

FIGS. 26A and 26C show perspective posterior views of the unadjusteddistal femoral alignment assembly shown in FIG. 25.

FIG. 26B shows a posterior perspective of the unadjusted distal femoralalignment assemblies shown in FIGS. 26A and 26C with the bone interfaceplate removed.

FIGS. 27-35 show an alternative method of aligning a knee surgeryaccording to embodiments of the invention.

FIG. 36 is a flow chart schematically illustrating a method for aligningand balancing a knee during knee surgery according to embodiments of theinvention.

FIG. 37 is a perspective view of a system for positioning a bone cuttingdevice on a femur, according to one embodiment of the present invention.

FIGS. 38A-38H are various views of an adjustable femoral attachmentportion of the system of FIG. 37.

FIGS. 39A-39N are various views of the system of FIG. 37, illustrating amethod of using the system, according to one embodiment of the presentinvention.

DETAILED DESCRIPTION

Embodiments of the present invention provide systems, devices, andmethods for facilitating the alignment and balancing of the knee duringknee replacement surgery and verifying such balance and alignment. Oncethe knee is properly aligned, a cut parallel to a previously made cut onthe tibia can be made on the distal femur. A prosthetic knee placed onthese cuts will maintain the proper alignment of the knee.

Referring now to FIG. 1, a distal femoral alignment assembly orcomponent 100 according to embodiments of the invention is shown in anexploded view. As shown in FIG. 1, distal femoral alignment assembly 100can be used for either the left or right knee, i.e., one side of thedistal femoral alignment assembly may be the medial side while the otheris the lateral side and vice versa. Distal femoral alignment assembly100 comprises a main body 101, an adjustable medial femoral portioncoupled to the main body, and an adjustable lateral femoral portioncoupled to the main body. When the distal femoral alignment assembly 100is coupled to a distal femur, the main body or stationary portion of thedistal femoral alignment assembly is generally stationary with respectto the adjustable medial and lateral femoral portions. The adjustablemedial and lateral femoral portions are adjusted with respect to themain body. Adjustable medial and lateral femoral portions respectivelycomprise medial and lateral paddles 102, 103. The medial and lateralpaddles each comprise anti-rotation shafts 104, 105 which fit into slots106 of the main body. Medial and lateral distraction screws 107, 108respectively couple the medial and lateral paddles 102, 103 with themain body 101. Distraction screw capture pegs 109, 110 fix the axialposition of the distraction screws 107, 108 relative to the main body101 such that rotation of the medial and lateral distraction screws onlyadjusts the positions of the adjustable medial and lateral femoralportions with respect to the main body 101. The main body comprisesmounts for attachment of a force sensor 111.

Referring now to FIG. 2, the main body 101 of the distal femoraladjustment assembly 100 further defines cutting guide locating apertureson its medial 113 a-c and lateral 112 a-c sides. These apertures arecutting guide locating means, e.g., by facilitating the placement ofplacement pins from which provide points of reference for the placementof a cutting guide. The main body further defines slots or verificationattachment slots or apertures 114 a, 114 b for attaching a kneealignment verification means as described below.

FIGS. 2 and 4 show the distal femoral adjustment assembly 100unadjusted. FIGS. 3 and 5 show the distal femoral adjustment assembly100 adjusted, i.e., the position of one paddle of the distal femoraladjustment assembly has been moved relative to the other.

FIGS. 6 and 7 show a perspective view of a knee alignment system 99 aaccording to embodiments of the invention. The system comprises thedistal femoral adjustment assembly 100 as described above. The systemfurther comprises a electronic force-sensing means or force sensor 115coupleable with the distal femoral adjustment assembly 100. As shown,the force sensor 115 comprises a handheld tool but may alternatively bea smaller device coupleable with the main body of the distal femoraladjustment assembly 100. The force sensor 115 senses the force betweenthe medial portion of the distal femur and the medial portion of thetibial plateau as well as the force between the lateral portion of thedistal femur and the lateral portion of the tibial plateau, for example,by comprising first and second force sensing portions 116 a, 116 b, thefirst force sensing portion 116 a being a lateral force sensing portionwhile the second 116 b is a medial force sensing portion and vice versa.The distal femur and tibial plateau are not shown in FIGS. 6-7. Theforce sensor 115 may be similar to those described U.S. PatentApplications Nos. 61/090,535 entitled “Sensing Force During Partial andTotal Knee Replacement Surgery” (Attorney Docket No. 021976-000800US)and 61/107,973 entitled “Dynamic Knee Balancing for Revision Procedures”(Attorney Docket No. 021976-000700US), the entireties of which had beenpreviously incorporated herein by reference.

FIG. 8 shows a visual display 117 coupleable with the force sensor 115.The visual display displays data representative of the force sensed bythe force sensor and may be similar to those described in U.S. patentapplication Ser. Nos. 10/973,936, now U.S. Pat. No. 7,578,821, entitled“Dynamic Knee Balancer with Pressure Sensing” (Attorney Docket No.021976-000210US); 61/090,535 entitled “Sensing Force During Partial andTotal Knee Replacement Surgery” (Attorney Docket No. 021976-000800US);and 61/107,973 entitled “Dynamic Knee Balancing for Revision Procedures”(Attorney Docket No. 021976-000700US), the entireties of which had beenpreviously incorporated herein by reference.

FIGS. 9-23 show a method of using an exemplary knee alignment systemduring knee replacement surgery according to embodiments of theinvention. As shown in FIGS. 9 and 11, the force sensor 115 is coupledto the distal femoral alignment assembly 100. As shown in FIGS. 10 and12, the distal femoral alignment assembly 100 and the coupled forcesensor 115 are placed in the gap 120 between the distal femur 118 andthe tibial plateau 121 of the knee. As shown in FIG. 13, the forcesensor 115 senses the forces between the lateral and medial portions ofthe distal femur and the tibial plateau. The visual display 117 showsthe sensed forces (as an example, the display shows the forcesunbalanced). An adjustment wrench 122 is coupled to a rotatabledistraction screw 107 of the distal femoral alignment assembly 100. Asshown in FIG. 14, when the unadjusted distal femoral alignment assembly100 and the coupled force sensor 115 are first placed in the gap 120between the distal femur 118 and the tibial plateau 121, the knee may bemisaligned, i.e., the femoral axis and the tibial axis are not alignedwith each other as in a normal knee. As shown in FIG. 14, the bottomsurface of the distal femoral alignment assembly is 80.degree. relativeto the mechanical axis 123 of the femur 118. As shown in FIG. 15, atleast one of the rotatable screws 107, 108 is rotated with theadjustment wrench 122 to adjust the relative position of the adjustablemedial and/or femoral portions and to correct the alignment of the knee.Generally, by balancing the sensed forces in the medial and lateralportions of the knee, correct alignment of the knee can be achieved (asshown in the visual display). For example, as shown in FIG. 16, thedistal femoral alignment assembly 100 has been adjusted so that thebottom surface of the distal femoral alignment assembly is 85.degree.relative to the mechanical axis 123 of the femur 118.

The system will typically further comprise a knee alignment verificationmeans to verify the alignment of the knee by verifying the angle formedby the mechanical axes of the femur and tibia. As shown in FIGS. 17 and18, the knee alignment verification means may be a laser knee alignmentverification member 124 coupleable to the main body of the distalfemoral alignment member 100. As shown in FIG. 18, the laser kneealignment verification member 124 emits a femoral laser beam 125 a to bealigned along the mechanical axis 123 a of the femur and a tibial laserbeam 125 b to be aligned along the mechanical axis 123 b of the tibia.The angle of the femoral laser beam and the tibial laser beam relativeto each other can be used by the surgeon to verify the proper anatomicalalignment of the knee, i.e., the angle between the mechanical axes 123a, 123 b of the femur and tibia. Alternatively, as shown in FIGS. 19 and20, the knee alignment verification means may be a mechanical kneealignment verification assembly 126. The mechanical knee alignmentverification assembly 126 comprises a mechanical knee alignmentverification hub 127, a femoral alignment rod 128 coupleable with thehub 127, and a tibial alignment rod 129 coupleable with the hub 127. Thecoupled femoral alignment rod 127 can be aligned along the mechanicalaxis 123 a of the femur 118. The coupled tibial alignment rod 129 can bealigned along the mechanical axis 123 b of the tibia 119. The angle ofthe femoral alignment rod 128 and the tibial alignment rod 129 relativeto each other can be used by the surgeon to verify proper alignment ofthe knee.

As shown in FIG. 21, the system may further comprise a plurality oflocating pins 130 a, 130 b. When the knee is properly aligned, at leastone locating pin (130 a and/or 130 b) may be placed on the medial sideof the distal femur 118 and at least one locating pin may be placed onthe lateral side of the distal femur as guided by the apertures of thedistal femoral alignment assembly. As shown in FIG. 22, once thelocating pins 130 a, 130 b are placed on the distal femur 118, thedistal femoral alignment assembly 100 may be disengaged from the distalfemur.

As shown in FIG. 23, the system may further comprise a distal femoralcutting guide 131 which can be coupled to the distal femur 118 andpositioned based on the position of the locating pins 130 a, 130 b. Cutsare made on the distal femur 118, for example, with a surgical sawblades 132. Typically, these cuts will form the basis for positioning ofthe femoral portion of an artificial knee. Exemplary surgical saw bladeswhich may be used to make these cuts on the distal femur are describedco-assigned U.S. Pat. Nos. 6,022,353; 6,503,253; and 6,723,101, theentire contents of which are incorporated herein by reference.

Referring now to FIGS. 24A-B, an alternative distal femoral alignmentsystem 99 b is shown including cutting guide 131 for making aprovisional cut on the distal femur in order to mount the distal femoralalignment assembly 100 flush against the provisionally cut distal femur.As shown in FIG. 25, angular graduation marks 133 are provided. Thegraduation marks correspond to movement created by adjusting either themedial or lateral distraction paddles 102, 103 as shown in FIG. 26B. Forclarity purposes, a right distal femur is shown in FIGS. 27-28 and 34-35and a right knee joint with femur and tibia is shown in FIGS. 29-33. Themedial side of components or assemblies of the distal femoral alignmentsystem shown in FIG. 24 are hereby described either medial or lateralbased on their position when used on a right knee. Of course, theinvention can be used on the left and/or right knees. Convex shapedpivot fulcrums 500 a, 500 b are provided on the surfaces of thedistraction paddles 102, 103 which directly contact the provisionallycut distal femur when the distal femoral alignment assembly 100 ismounted against the distal femur 118. The curved surface of thedistraction paddles 102, 103 creates fixed distance fulcrum points todetermine how much angle is being adjusted. FIGS. 26A and 26C showanother embodiment of the distal femoral alignment assembly 100 of thealternative distal femoral alignment system 99 b shown in FIG. 24, whichincludes bone interface plate 137. This plate 137 provides protectionfrom convex shaped distraction paddles 102 and 103 from indenting thesofter cancellous bone exposed as a result of a provisional cut beingmade on the distal femur 118 (not shown in FIG. 26). FIG. 26C shows thebone interface plate 137 sitting on top of convex shaped distractionpaddles 102 and 103 in their unadjusted position. Shoulder screw 138 isshown, which slips through a loosely fitted hole 139 in bone interfaceplate 137 to allow for tilting of bone interface plate 137 when convexshaped distraction paddles 102 and 103 are adjusted from theirunadjusted position to an adjusted position. Spacing between convexshaped adjustment paddles 102 and 103 is maintained in themedial-lateral direction to provide for a known pivot fulcrum betweenthe two convex shaped adjustment paddles, which corresponds to angulargraduations 133 shown in FIG. 25. The angular gradations provide anindication of the angle between the femur and tibia.

Referring now to FIGS. 27-35, a method of using an exemplary kneealignment system used during knee replacement surgery is shown accordingto embodiments of the invention. For purposes of clarity, a bone cut hasalready been made on the proximal tibia 119 prior to the methodsdescribed in FIGS. 27-35. FIG. 27 shows provisional distal femoralcutting guide 131 moveably attached to the provisionally cut distalfemur 118 via two pins 130 a and 130 b. FIG. 28 shows provisionalfemoral cutting guide 131 and pins 130 a and 130 b now having beenremoved and femoral anterior-posterior cutting guide 134 is nowremovably attached to distal femur 118. Saw blade 132 is shown and theanterior and posterior bone cuts are performed on distal femur 118. FIG.29 shows now the “extension gap” with the proximal tibial cut havingbeen made and a provisional distal femoral cut having been made. Theposterior femoral cut has also been made but hidden from view in FIG.29. The anterior cut has also been made on distal femur 118.

Moving now to FIG. 30, the distal femoral alignment assembly 100 andother components of the distal femoral alignment system 99 b are shownbetween the proximal tibia 119 and the distal femur 118, with the leg infull extension. Thickness adapter 133 is shown moveably coupled to forcesensor 115, and force sensor 115 is moveable coupled to distal femoralassembly 100. Adjustable posterior member 135 a is shown adjacent to alongitudinal slot 400 open on the posterior side of distal femoralassembly 100, with the slot closed on the anterior side of the distalfemoral assembly 100. FIG. 31 shows adjustable posterior member 135 ahaving now been moveably coupled within the longitudinal slot 400 alongthe medial side of distal femoral assembly 100. Moveable coupling means136 a, 136 b can include magnets or other common coupling means such asscrews or spring clips. Longitudinal slots are also provided on theopposite side of the distal femoral assembly 100. Longitudinal slotsalong the sides of distal femoral assembly 100 are of adequate length toallow for anterior-posterior adjustment of adjustable posterior memberto abut the previously made posterior cut 401 of the distal femur 118.The adjustable posterior members further balance extension filling theposterior space with a condylar thickness similar to the posteriorcondylar thickness of the femoral component to be implanted thus takinginto account soft-tissue tendencies, or bias. FIG. 32 shows componentsand assemblies of the distal femoral alignment system 99 b nowcompletely in place between the proximal tibia and the distal femur andforce readings coupled from force sensor 115 are being displayed ondisplay 117, It is understood that display 117 may be integral to forcesensor 115. The display 117 can also be separable from the sensor. Thedisplay 117 is showing force readings of 5 and 2 lateral and medialrespectively, indicating lower force between the medial side of thedistal femur and the medial side of the proximal tibia, in this example.Adjustment wrench 122 is shown in line with the medial distraction screw107. FIG. 33 shows the medial distraction paddle 102 having now beenadjusted to a point wherein the forces being measured by sensor 115 anddisplayed by display 117 read 5 on both the lateral and the medial side.Pin 130 a is shown being driven through a lateral side cutting guidelocating aperture and pin 130 b has yet to be driven through the medialside cutting guide locating aperture. FIG. 34A shows both pins havingnow been driven through cutting guide locating apertures of distalfemoral assembly 100, and distal femoral assembly 100 now having beenremoved from the distal femur 118. Cutting guide 131 b is positionedover pins 130 a and 130 b. FIG. 34B shows cutting guide 131 b nowpositioned over pins 130 a and 130 b and saw blade 132 will be used tomake the final distal femoral cut at an angle “A” which is the plane ofbalanced resection as determined by the force sensor. FIG. 35 showsfemoral anterior-posterior cutting guide 134 now removably coupled todistal femur 118 and saw blade 132 is shown making a final cut on theanterior distal femur. Anterior and posterior chamfer cuts will also bemade on the distal femur 118 at this point.

Referring now to FIG. 37, in another embodiment of the invention, asystem 200 for positioning a bone cutting guide on a femur during kneesurgery is shown. System 200 may generally include an adjustable femoralattachment member 202, a cutting guide 208, and a force sensor 212coupled with a display 216. Femoral attachment member 202, which isdescribed in further detail below, may include a stationary portion 204,which attaches in a fixed way to the femur F, and an adjustable portion206, which moves relative to stationary portion 204 to create a spacebetween the two portions on the lateral, medial or both sides of theknee joint. Attachment member 202 may include a single adjustment member218 for adjusting adjustable portion 204 and medial and lateralelevators (also not visible in FIG. 37) for creating a medial spaceand/or a lateral space in the joint. System 200 may also include a slidemember 210 for attaching to cutting guide 208 to facilitate itsattachment to adjustable femoral attachment member 202. Finally, system200 may further include an insert 214 (or multiple inserts) to bepositioned between femoral attachment member 202 and sensor 212. Inserts214 of various thicknesses may be provided, so that a physician canselect a desired amount of initial tension within the knee. In variousembodiments, inserts 214 may be removably attachable to sensor 212.

In FIG. 37, system 200 is shown in position within a knee joint, betweena cut distal end of a femur F and a cut proximal end of a tibia T, wherean anterior cut AC has also been made to the femur F. (A posterior cutis also typically made prior to inserting system 200 in the knee, butthe posterior aspect of the femur F is not visible in FIG. 37.) In thisembodiment, system 200 will be described for use in a knee where initialdistal, anterior and posterior bone cuts have been made on the femur Fand where at least an initial bone cut has been made on the proximal endof the tibia T. In alternative embodiments, however, it may be possibleto use system 200 in a knee surgery procedure in which fewer (or no)initial bone cuts have been made.

In brief summary, system 200 may be used in a knee surgery procedure tofacilitate and/or improve upon positioning of bone cutting guide 208 onthe femur F in order to make a bone cut on a distal end of the femur F.As will be described in greater detail below, system 200 may be placedwithin the knee joint, and femoral attachment member 202 may be adjustedto create a space, and thus increase tension, on either the medial sideof the knee or the lateral side of the knee, to balance forces withinthe joint. Forces may be sensed by sensor 212 and displayed on display216. As femoral attachment member 202 is adjusted, cutting guide 208moves along with attachment member 202 and changes its angle oforientation relative to the distal femur F. When sensed forces withinthe knee are balanced, cutting guide 208 may be fixed to the femur F,and the femoral bone cut may be made.

One improvement of system 200 is that it can remain in place within theknee joint while the knee moves through a range of motion betweenflexion and extension. Another improvement is that both the medial sideand the lateral side of femoral attachment member 202 may be adjustedusing the same adjustment member 218. Furthermore, system 200 is lowprofile, so is easier to insert into the joint space than at least someprior art systems. Also, system 200 may be used on a femur F afterinitial bone cuts have been made, unlike some systems designed for usewith an uncut femur.

Referring now to FIGS. 38A-38H, a number of different views ofadjustable femoral attachment member 202 are shown. As previouslymentioned, femoral attachment member 202 generally includes stationaryportion 204, which attaches in a fixed manner to the cut distal end of afemur, and adjustable portion 206, which moves relative to stationaryportion 204 to increase the space between the distal femur and proximaltibia on the medial or lateral side of the knee. Stationary portion 204includes a platform 220, for contacting the cut distal end of the femur,and screw holes 236, through which screws are advanced to attachstationary portion 204 to the femur. Stationary portion 204 is removedfrom FIGS. 38C, 38D, 38F and 38G so that other parts of femoralattachment member 202 may be more easily visualized.

FIGS. 38A-38D provide various views of adjustable femoral attachmentmember 202 in an unadjusted configuration. Adjustable portion 206 ofadjustable femoral attachment member 202 may include left and right (or“lateral” and “medial”) condylar members 207 a, 207 b, an elevatoradjuster 222, a cutting guide attachment post 237 along which cuttingguide 208 slides to contact a femur, and adjustment member 218.Stationary portion 202 may include platform 220, as already mentioned.In FIGS. 38C and 38D, platform 220 is removed to better show elevatoradjuster 222, a lateral (or “left”) elevator 224 and a medial (or“right”) elevator 226 of adjustable portion 206.

As shown in FIGS. 38C and 38D, each elevator 224, 226 has a slopedbottom surface 225, 227 on one end of its bottom side, and each elevator224, 226 fits into a slot 221 a, 221 b on adjustable portion 206. As isvisible in FIG. 38C, each slot 221 a, 221 b includes a sloped surface atone end, over which the sloped surface 225, 227 of its correspondingelevator 224, 226 rides. Elevator adjustor 222 sits over elevators 224,226 and is moved back and forth along slots 221 a, 221 b by adjustingadjustment member 218. When moved in one direction, elevator adjustor222 pushes one of elevators 224 up a slope of its corresponding slot 221a. When moved in the opposite direction elevator adjustor 222 pushes theother elevator 226 up a slope of its corresponding slot 221 b. Elevators224, 226, when elevated, push against platform 220, causing it to riseon one side or the other, thus creating space between adjustable portion206 and stationary portion 204, and thus increasing tension (and thussensed force) on that side of the joint. By this mechanism, system 200is able to make medial and/or lateral tension adjustments using only oneadjustment member 218.

Referring now to FIGS. 38E and 38F, femoral attachment member 202 isshown after elevator 226 has been elevated to raise platform 220 andthus create a space 230. Space 230 will thus increase a distance betweena femur and a tibia on one side of the knee (either the lateral ormedial side, depending on what knee system 200 is being used on). FIG.38F shows attachment member 202 with platform 220 removed, so that theraised elevator 226 is visible. Elevator 226 may be raised, for example,by turning adjustment member 218 in a first direction (clockwise orcounter-clockwise in alternative embodiments).

FIGS. 38G and 38H show femoral attachment member 202 after elevator 224has been elevated to raise platform 220 and thus create a space 232 onthe opposite side of attachment member 202. Space 232 will increase adistance between the femur and the tibia on the opposite side of theknee as that previously discusses (either the lateral or medial side,depending on what knee system 200 is being used on). FIG. 38H showsattachment member 202 with platform 220 removed, so that the raisedelevator 224 is visible. Elevator 224 may be raised by turningadjustment member 218 in the opposite direction of that used to raiseelevator 226.

Turning now to FIGS. 39A-39N, a method for using system 200 to make abone cut on a distal femur F will be described. Prior to the step shownin FIG. 39A, a proximal cut is made to the tibia T, and an initialdistal cut DC, anterior cut AC and posterior cut (not visible) are madeto the femur F. Force sensor 212 and insert 214 may then be positionedon the cut proximal end of the tibia T, and femoral attachment member202 may be attached to the cut distal end of the femur F via screws 234advanced through screw holes 236 of stationary portion 204. Stationaryportion 204 of femoral attachment member 202 is thus fixedly attached tothe femur F, and adjustable portion 206 is adjustable relative tostationary portion 204 to adjust medial and/or lateral tension in theknee. Femoral attachment member 202 is typically attached in such a waythat condylar portions 207 a, 207 b (barely visible in FIG. 39A) abutthe cut posterior surfaces of the femur F. The order in which forcesensor 212, insert 214 and attachment member 202 are positioned in theknee joint is not critical to any given embodiment, and the method isnot limited to positioning in any particular order. As illustrated inFIG. 39A, the various components of system 200 may be inserted into theknee joint while the knee is in flexion. This is an improvement oversome systems which must be inserted with the knee in extension.

Visible in FIG. 39A are cutting guide attachment post 237 and a bottomsurface of elevator adjustor 222, both of which are parts of adjustablefemoral attachment member 202. Cutting guide attachment post 237provides structure for attachment of cutting guide 208 to femoralattachment member 202. The bottom surface of elevator adjustor 222, atleast in one embodiment, may be used to display to a user an amount ofangular adjustment that has been made to attachment member 202. Thesefunctions will be described in greater detail below. Also illustrated isdisplay 216, which includes a lateral force indicator 217 a (or “leftforce indicator”) and a medial force indicator 217 b (or “medial forceindicator”). Indicators 217 a, 217 b may have any suitable numerical orletter scheme, such as numbers between 0 and 20, letters from A throughM, or the like. In some embodiments, the numbers may relate to Newtonsof force measured by sensor 212.

FIG. 39B illustrates cutting guide 208 and slide member 210 in greaterdetail. Cutting guide 208 may include multiple pin apertures 240,through which pins may be advanced to attach cutting guide 208 to thefemur F, a saw blade slot 242, through which a surgical saw blade isadvanced to make a bone cut. Cutting guide 208 and slide member 210 areattached to one another via a screw 238 or via other means inalternative embodiments.

As shown in FIG. 39C, cutting guide 208 and slide member 210 may beadvanced over guide attachment post 237 until cutting guide 208 contactsthe anterior cut portion AC of the femur F.

As illustrated in FIGS. 39D and 39E, after desired advancement isachieved, screw 238 may be turned, using an adjustment device 244, toaffix slide member 210 to guide attachment post 237 of femoralattachment member 202. This tightening will also secure cutting guide208 to the anterior cut bone surface AC. In one embodiment, adjustmentdevice 244 may be used to adjust both screw 238 and adjustment member218. In alternative embodiments, two different adjustment devices 244may be provided.

Referring to FIG. 39F, the knee may next be moved into extension, withsystem 200 in place in the joint. At this point, medial and lateralforces are sensed and displayed on display 216 as lateral indicator 217a and medial indicator 217 b. As seen here, the medial and lateralforces are often out of balance (here represented by the numbers “6” and“8” on indicators 217 a, 217 b. Adjustment device 244 may then be usedto adjust adjustment member 218 to raise either lateral elevator 214 ormedial elevator 216 to at least approximately balance the medial andlateral forces. In various embodiments, adjustment device 244 may be awrench, as shown, or any other suitable device, such as a screw driveror the like. Generally, a physician will raise one of elevators 214, 216sufficiently to balance the measured forces in the knee, which aredisplayed on display 216.

Now referring to FIG. 39G, once medial and lateral forces are balancedas desired (see indicators 217 a, 217 b each reading “8”), pins 246 maybe advanced through pin apertures 240 to attach cutting guide 208 to thefemur F. As shown in FIG. 39H, the knee may then be moved back intoflexion. As shown in FIGS. 39H and 39I, at this point, a reference mark248 on the bottom surface of elevator adjustor 222 may be used inconjunction with indicator marks 252, 254, to approximate an amount ofangular adjustment that has been made to femoral attachment member 202and thus to cutting guide 208. In other words, reference mark 248 andindicator marks 252, 254 may allow a physician to approximate an angleof resection that cutting guide 208 will make on the distal end of thefemur F when the cut is made. Each indicator mark 252, 254, for example,may indicate a degree of resection angle. For example, indicator marks252 may indicate a lateral resection angle, and indicator marks 254 mayindicate a medial resection angle. If reference mark 248 is located atthe midpoint between the two end indicator marks 252, 254, this coulddesignate a resection angle of approximately 0 degrees. The exampleshown in FIGS. 39H and 39I may designate a medial resection angle ofabout 2.5 degrees. Of course, in alternative embodiments, differentnumbers, gradations and/or configurations of reference mark 248 andindicator marks 252, 254 may be used. In other alternative embodiments,this step may be skipped, and system 200 may not include any referencemark 248 or indicator marks 252, 254.

With reference now to FIGS. 39J-39M, femoral attachment member 202 andslide member 210 may now be removed from the knee, leaving cutting guide208 attached to the femur F. As shown in FIG. 39J, screws 234 may beremoved from stationary portion 204. Next, as in FIG. 39K, adjustmentdevice 244 may be turned to loosen slide member 210, which then may beremoved from cutting guide 208 and post 237, as illustrated in FIG. 39L.Finally, as illustrated in FIG. 39M, adjustable femoral attachmentmember 202, sensor 212 and insert 214 may all be removed from the knee,leaving only cutting guide 208 and pins 246 attached to the femur F.

As illustrated in FIG. 39N, with cutting guide 208 in a desired positionfor guiding a distal femoral bone cut, a bone saw handpiece 260 with sawblade assembly 262 may be used to make the bone cut. In someembodiments, saw blade assembly 262 will be guided by passing throughslot 242, which will be oriented in a desired position based on theadjustments described above.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting in scope of the invention which is defined by the appendedclaims.

1. A system for positioning a cutting guide on a femur of a knee to makea cut along a distal end of the femur during a surgical procedure on theknee, the system comprising: an adjustable femoral attachment memberconfigured to attach to a cut distal end of the femur, the femoralattachment member comprising: a medial elevator for increasing an amountof space between a medial portion of the femoral attachment member andthe cut distal end of the femur; a lateral elevator for creating spacebetween a lateral portion of the femoral attachment member and the cutdistal end of the femur; and a single adjustment member configured toadjust both the medial and lateral elevators; a cutting guide removablyattachable to the femoral attachment member and configured to guide asurgical saw to make an additional cut on the distal end of the femur;and a force sensor for positioning between the femoral attachment memberand a proximal end of a tibia of the knee, wherein the force sensorcomprises a medial portion for sensing a medial force in the knee and alateral portion for sensing a lateral force in the knee.
 2. A system asin claim 1, further comprising an insert for positioning between theforce sensor and the femoral attachment member in the knee.
 3. A systemas in claim 1, further comprising multiple pins for attaching thecutting guide to the femur.
 4. A system as in claim 1, furthercomprising multiple screws for attaching the femoral attachment memberto the femur.
 5. A system as in claim 4, wherein the femoral attachmentmember comprises at least two screw holes on a distal-facing surface foraccepting the screws.
 6. A system as in claim 5, further comprising anindicator on the distal-facing surface for indicating an angle ofresection to which the cutting guide has been adjusted.
 7. A system asin claim 1, further comprising an adjustment device for adjusting thefemoral attachment member.
 8. A system as in claim 7, wherein theadjustment device comprises a wrench configured to turn the adjustmentmember in one direction to adjust the medial elevator and in an oppositedirection to adjust the lateral elevator.
 9. A system as in claim 1,further comprising a slide member removably coupled with the cuttingguide so that the cutting guide and slide member can slide onto thefemoral attachment member to contact an anterior side of the femur. 10.A system as in claim 1, wherein the femoral attachment member isconfigured to be attached to the cut distal end of the femur while theknee is in flexion.
 11. A system as in claim 10, wherein the femoralattachment member is configured to remain attached to the cut distal endof the femur while the knee is moved from flexion to extension.
 12. Asystem as in claim 1, further comprising a display coupled with thesensor and configured to display a first indicator representing themedial force and a second indicator representing the lateral force. 13.A method for positioning a cutting guide on a femur of a knee to make acut along a distal end of the femur during a surgical procedure on theknee, the method comprising: attaching an adjustable femoral attachmentmember with a cut distal end of the femur; positioning a force sensor ona cut proximal end of a tibia of the knee; attaching the cutting guideto the femoral attachment member; adjusting the femoral attachmentmember, using a single adjustment member of the femoral attachmentmember, to elevate at least one of a medial side and a lateral side ofthe femoral attachment member relative to the cut distal end of thefemur to approximately balance medial and lateral forces displayed on adisplay coupled with the sensor, wherein adjusting the femoralattachment member changes a position of the cutting guide relative tothe femur; and attaching the cutting guide to the femur.
 14. A method asin claim 13, wherein attaching the femoral attachment member comprisesadvancing two screws through holes in the attachment member and into thecut distal end of the femur while the knee is in flexion.
 15. A methodas in claim 14, further comprising positioning an insert between theforce sensor and the femoral attachment member.
 16. A method as in claim14, further comprising moving the knee into extension while the femoralattachment member remains attached to the femur and before adjusting thefemoral attachment member.
 17. A method as in claim 16, wherein thecutting guide is attached to the femur while the knee is in extension.18. A method as in claim 17, wherein attaching the cutting guidecomprises pinning the cutting guide to the femur using multiple pins.19. A method as in claim 17, further comprising moving the knee backinto flexion after the cutting guide is attached.
 20. A method as inclaim 19, further comprising viewing a resection angle indicator on adistal surface of the femoral attachment member while the knee is inflexion, wherein the resection angle indicator indicates approximatelyan angle of resection of the distal femur based on a position of thecutting guide.
 21. A method as in claim 13, wherein attaching thecutting guide to the femoral attachment member comprises sliding thecutting guide, attached to a slide member, onto the femoral attachmentmember until the cutting guide contacts a cut anterior surface of thefemur.
 22. A method as in claim 21, further comprising, before attachingthe cutting guide to the femoral attachment member, attaching the slidemember to the cutting guide.
 23. A method as in claim 22, whereinattaching the slide member to the cutting guide comprises tightening afirst screw using an adjustment device, and wherein adjusting thefemoral adjustment member comprises turning a second screw using thesame adjustment device.
 24. A method as in claim 13, further comprising,before attaching the femoral adjustment member, making initial cuts onthe distal end of the femur, an anterior side of the femur and aposterior side of the femur.
 25. A method as in claim 13, wherein thesingle adjustment member comprises a screw, and wherein adjusting thefemoral adjustment member comprises using an adjustment device to turnthe screw in a first direction to adjust the medial side of theadjustment member and in a second direction to adjust the lateral sideof the adjustment member.
 26. A method as in claim 13, furthercomprising: removing the femoral attachment member from the femur andthe sensor from the tibia; and cutting the distal end of the femur,using the attached cutting guide.
 27. A method as in claim 26, furthercomprising removing a slide member attached to the cutting guide beforecutting the distal end of the femur.
 28. A method for making a cut on adistal end of a femur during a surgical procedure on a knee, the methodcomprising: attaching an adjustable femoral attachment member with thedistal end of the femur on which initial distal, anterior and posteriorcuts have previously been made, while the knee is in flexion;positioning a force sensor coupled with an insert on a cut proximal endof a tibia of the knee; sliding a cutting guide onto the femoralattachment member until it contacts a cut anterior side of the femur;tightening the cutting guide onto the femoral attachment member; movingthe knee into extension; adjusting the femoral attachment member, usinga single adjustment member of the femoral attachment member, to balancemedial and lateral forces displayed on a display coupled with thesensor, wherein adjusting the femoral attachment member changes aposition of the cutting guide relative to the femur; attaching thecutting guide to the femur; moving the knee into flexion; removing thefemoral attachment member from the femur; and making the cut on thedistal end of the femur, using the cutting guide.
 29. A method as inclaim 28, wherein adjusting the femoral attachment member comprisesturning the single adjustment member using an adjustment device in atleast one of a first direction, to adjust the medial force, and a seconddirection, to adjust the lateral force.
 30. A method as in claim 29,wherein tightening the cutting guide comprises using the adjustmentdevice to tighten a screw attaching the cutting guide to the femoralattachment member.
 31. A method as in claim 28, wherein sliding thecutting guide onto the femoral attachment member comprises sliding aslide member attached to the cutting guide along the femoral attachmentmember, wherein the method further comprises removing the slide memberfrom the cutting guide before making the cut on the distal end of thefemur.
 32. A method as in claim 28, further comprising viewing aresection angle indicator on the femoral attachment member after movingthe knee into flexion to approximate a resection angle before making thecut.
 33. A method as in claim 28, further comprising removing the sensorand the insert from the tibia before making the cut on the distal end ofthe femur.
 34. A device for positioning a cutting guide on a femur of aknee during a surgical procedure on the knee, the device comprising: astationary femoral member that attaches to a cut distal end of thefemur; an adjustable femoral member moveably attached to the stationaryfemoral member; a medial elevator for creating space between thestationary and adjustable femoral members closer to a medial edge of thedevice than a lateral edge of the device; a lateral elevator forcreating space between the stationary and adjustable femoral memberscloser to the lateral edge of the device than the medial edge of thedevice; and a single adjustment member configured to adjust both themedial and lateral elevators.
 35. A device as in claim 34, furthercomprising a cutting guide removably attachable to the adjustablefemoral member and configured to guide a surgical saw to make anadditional cut on the distal end of the femur.
 36. A device as in claim34, further comprising a force sensor for positioning between theadjustable femoral member and a proximal end of a tibia of the knee,wherein the force sensor comprises a medial portion for sensing a medialforce in the knee and a lateral portion for sensing a lateral force inthe knee.
 37. A device as in claim 36, further comprising a displaycoupled with the sensor and configured to display a first indicatorrepresenting the medial force and a second indicator representing thelateral force.
 38. A device as in claim 36, further comprising an insertfor positioning between the force sensor and the femoral attachmentmember in the knee.
 39. A device as in claim 34, further comprisingmultiple screws for attaching the stationary femoral member to thefemur.
 40. A device as in claim 34, further comprising an indicator on adistal-facing surface of the adjustable femoral member for indicating anangle of resection to which the cutting guide has been adjusted.
 41. Adevice as in claim 34, further comprising an adjustment device foradjusting the medial and lateral elevators via the single adjustmentmember.
 42. A device as in claim 41, wherein the adjustment devicecomprises a wrench configured to turn the adjustment member in onedirection to adjust the medial elevator and in an opposite direction toadjust the lateral elevator.
 43. A device as in claim 34, wherein thesingle adjustment member comprises a sliding portion that slides in afirst direction to elevate the medial elevator and in a second, oppositedirection to elevate the lateral elevator.
 44. A device as in claim 34,wherein the device is configured to be attached to the cut distal end ofthe femur while the knee is in flexion.
 45. A device as in claim 44,wherein the femoral attachment member is configured to remain attachedto the cut distal end of the femur while the knee is moved from flexionto extension.